Oil can be recovered from oil-bearing reservoirs by a number of well-known drilling methods. Wellbore fluids, also known as drilling fluids, are employed in these methods, and are generally circulated down the hole being drilled and around the drill bit. Wellbore fluids are used in the construction, repair and treatment of wellbores.
The fluids serve many purposes, including cooling and lubricating the drill bit and carrying drilling cuttings away from the bit. Additionally, the wellbore fluids can contain materials that control the viscosity of the fluid, provide for good heat transfer and lubricity, and allow for optimal environmental performance. They can also include materials that help to prevent fluid loss into the geological formations through which the drill bit passes.
PCT Publication WO 2007/088322 discloses wellbore fluids comprising a base fluid and a particulate bridging agent.
Wellbore fluids that are environmentally benign, cost-effective and have enhanced functionality are desired.